The invention relates to surface preparation, cleaning, rinsing and drying of workpieces, such as semiconductor wafers, flat panel displays, rigid disk or optical media, thin film heads, or other workpieces formed from a substrate on which microelectronic circuits, data storage elements or layers, or micro-mechanical elements may be formed. These and similar articles are collectively referred to here as a xe2x80x9cwaferxe2x80x9d or xe2x80x9cworkpiecexe2x80x9d.
The semiconductor manufacturing industry is constantly seeking to improve the processes used to manufacture microelectronic circuits and components, such as the manufacture of integrated circuits from wafers. The objectives of many of these improved processes are decreasing the amount of time required to process a wafer to form the desired integrated circuits; increasing the yield of usable integrated circuits per wafer by, for example, decreasing contamination of the wafer during processing; reducing the number of steps required to create the desired integrated circuits; and reducing the costs of manufacture.
In the processing of wafers, it is often necessary to subject one or more sides of the wafer to a fluid in either liquid, vapor or gaseous form. Such fluids are used to, for example, etch the wafer surface, clean the wafer surface, dry the wafer surface, passivate the wafer surface, deposit films on the wafer surface, etc. Controlling how the processing fluids are applied to the wafer surfaces, is often important to the success of the processing operations.
Various machines and methods have been used for carrying out these manufacturing processes. However, existing machines have several disadvantages. These disadvantages include relatively large consumption of process chemicals and water. This consumption of process chemicals increases manufacturing costs, which ultimately increases the cost of the final product, such as e.g., computers, cell phones, and virtually all types of consumer, industrial, commercial and military electronic products. In addition, many process chemicals are toxic and require special handling, storage, and disposal methods. These can be costly and difficult, but are necessary for health, safety and environmental reasons. Consequently, reducing consumption of process chemicals has many advantages.
Reducing consumption of water is also beneficial. In many areas, water is becoming increasingly scarce. Due to population growth, there is greater competition for water. Disposing of waste water in environmentally friendly ways has also often become more difficult or costly. Accordingly, reducing water consumption in the manufacturing process is also important.
In many process manufacturing steps, the process chemicals used should be applied evenly onto the wafers, to avoid having too much or too little etching, film removal, etc. Existing machines often are not able to sufficiently uniformly apply process chemicals. This can result in lower yields. Moreover, many existing machines try to compensate for variations in applying process chemicals by using larger amounts of process chemicals. This inefficient use of process chemicals leads to the disadvantages described above.
In general, it is advantageous to rapidly remove a process fluid from a process chamber, so that a next step may be performed without delay. Fast draining or removing of a process liquid speeds up the manufacturing sequence. In many process machines, removing used liquid at the end of a process step can be a relatively time consuming step. Typically, the liquid must be drained out of one or more drain openings which are limited in size to achieve desired liquid flow or containment characteristics during processing. While waiting for the liquid to drain or be removed, the process machine, or potentially even a larger system having the process machine as one of several machines, is inactive. Consequently, processing is slowed due to the wait time for removing fluid.
Accordingly, improved machines and methods which provide improved yield, consume less process chemicals and water, and offer better results in performing manufacturing operations, are needed.
In a first aspect, a process head for holding a workpiece is supported on a head lifter or elevator. The process head is brought into engagement with a base having a bowl for holding a bath of liquid. A drain is provided at a perimeter of the bowl. The bowl advantageously has a substantially uniform radius, except at a contour section where the radius increases as it approaches the bowl outlet or drain. The contour section minimizes retention of liquid within the bowl, providing for faster and more effective draining or removal of liquid from the bowl. This allows for faster manufacturing as well as reducing potential for loss of workpieces due to contamination.
In a second aspect, a single drain opening is provided at the perimeter of the bowl. A valve manifold block connected to the drain outlet is switchable to direct liquid flowing out of the bowl drain to selected collection, re-circulation or waste line locations. Gas spray nozzles may be associated with the drain to assist in moving liquid out of the drain. These features allow for faster manufacturing as liquid can be removed more quickly. It may also reduce consumption of water and process chemicals by allowing recirculation with less unintended mixing of fluids used in sequential process steps.
In a third aspect, a process apparatus has a process head having a load/unload position, a process position, and also a fast drain position. The apparatus preferably includes a lower rotor which rotates with an upper rotor and a workpiece. In the load position, the upper and lower rotors are spaced apart. In the process position, the upper and lower rotors are brought together and contact and preferably also seal adjacent to their outer edges. In the fast drain position, the upper and lower rotors are moved apart slightly, to create a circumferential opening between them. With the rotors and workpiece spinning, fluids on or around the workpiece are quickly centrifugally removed. As the circumferential opening is large in comparison to the drain openings which may be used in one or both rotors, draining or fluid removal is very fast, and even up to 10 or more times faster than in the machines currently in use. These features allow for faster processing of workpieces.
Accordingly, it is an object of the invention to provide improved methods and apparatus for processing a workpiece. The invention resides as well in subcombinations of the steps and features described. The features described and illustrated in connection with one embodiment may or course be used in other embodiments as well.